Transmission (conventional and high voltage) electron microscopy of the optic neuropiles and peripheral retina of the house fly continued in order to develop a neuronal blueprint. Freeze fracture/etch (FF) technique is also used to characterize membrane specializations that might effect intercellular communication. Nearly a score of thick section series have been accomplished by HVEM (both cross and longitudinal directions in the lamina). Each series represents about 10 micron of tissue transversed and about 30 micrographs. These data will be used in basic reconstruction and will be compared to a similar number of thin sectioned series and views of freeze fracture planes. Fly retina has a variety of membrane specialization (gap, septate and continuous-like junctions). A new intercellular junction was discovered between retinular cells characterized by indistinct septa in the intermembrane cleft. Correlations of this specialization were found in FF preparations. Mitochondria lined up along these junctions often within 90 Angstroms of the unit membrane. This membrane specialization has characteristics of tight and continuous junctions. A possible function of this desmosome may be in enforcing the ommatidial twist and maintaining localized concentration gradients between photoreceptor cells.